Capacitor assembly and associated method

ABSTRACT

A capacitor assembly for use in, and a method of assembling, a filtered feedthrough. The capacitor includes an insulative member fixedly attached to its bottom portion to inhibit high voltage arcing. The termination material present on the inner and outer diameters of the capacitor is absent from a portion of the capacitor proximate the bottom portion, e.g., at the insulative member.

RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.12/436,392, filed May 6, 2009 entitled “CAPACITOR ASSEMBLY ANDASSOCIATED METHOD”, herein incorporated by reference in its entirety.

FIELD

The present disclosure relates to a capacitor assembly and associatedmethod of assembling a filtered feedthrough for implantable medicaldevices and, more particularly, to a method in which a capacitorassembly that inhibits high voltage arcing is utilized.

INTRODUCTION

The background description provided herein is for the purpose ofgenerally presenting the context of the disclosure. Work of thepresently named inventors, to the extent the work is described in thisbackground section, as well as aspects of the description that may nototherwise qualify as prior art at the time of filing, are neitherexpressly nor impliedly admitted as prior art against the presentdisclosure.

Electrical feedthroughs serve the purpose of providing an electricalcircuit path extending from the interior of a hermetically sealedcontainer to an external point outside the container. A conductive pathis provided through the feedthrough by a conductor pin which iselectrically insulated from the container. Many feedthroughs are knownin the art that provide the electrical path and seal the electricalcontainer from its ambient environment. Such feedthroughs typicallyinclude a ferrule, the conductor pin or lead and a hermetic ceramic sealwhich supports the pin within the ferrule. Such feedthroughs aretypically used in electrical medical devices such as implantable pulsegenerators (IPGs). It is known that such electrical devices can, undersome circumstances, be susceptible to electromagnetic interference(EMI). At certain frequencies for example, EMI can inhibit pacing in anIPG. This problem has been addressed by incorporating a capacitorstructure within the feedthrough ferrule, thus shunting any EMI at theentrance to the IPG for high frequencies. This has been accomplishedwith the aforementioned capacitor device by combining it with thefeedthrough and incorporating it directly into the feedthrough ferrule.Typically, the capacitor electrically contacts the pin lead and theferrule.

Many different insulator structures and related mounting methods areknown in the art for use in medical devices wherein the insulatorstructure also provides a hermetic seal to prevent entry of body fluidsinto the housing of the medical device. The feedthrough terminal pins,however, are connected to one or more lead wires which effectively actas an antenna and thus tend to collect stray or electromagneticinterference (EMI) signals for transmission to the interior of themedical device. In some prior art devices, ceramic chip capacitors areadded to the internal electronics to filter and thus control the effectsof such interference signals. This internal, so-called “on-board”filtering technique has potentially serious disadvantages due tointrinsic parasitic resonances of the chip capacitors and EMI radiationentering the interior of the device housing.

In another approach, a filter capacitor is combined directly with aterminal pin assembly to decouple interference signals to the housing ofthe medical device. In a typical construction, a coaxial feedthroughfilter capacitor is connected to a feedthrough assembly to suppress anddecouple undesired interference or noise transmission along a terminalpin.

So-called discoidal capacitors having two sets of electrode platesembedded in spaced relation within an insulative substrate or basetypically form a ceramic monolith in such capacitors. One set of theelectrode plates is electrically connected at an inner diameter surface,e.g., with a termination material, of the discoidal structure to theconductive terminal pin utilized to pass the desired electrical signalor signals. The other or second set of electrode plates is coupled,e.g., with a termination material, at an outer diameter surface of thediscoidal capacitor to a cylindrical ferrule of conductive material,wherein the ferrule is electrically connected in turn to the conductivehousing or case of the electronic instrument.

In operation, the discoidal capacitor permits passage of relatively lowfrequency electrical signals along the terminal pin, while shunting andshielding undesired interference signals of typically high frequency tothe conductive housing. Feedthrough capacitors of this general type arecommonly employed in implantable pacemakers, defibrillators and thelike, wherein a device housing is constructed from a conductivebiocompatible metal such as titanium and is electrically coupled to thefeedthrough filter capacitor. The filter capacitor and terminal pinassembly prevent interference signals from entering the interior of thedevice housing, where such interference signals might otherwiseadversely affect a desired function such as pacing or defibrillating.

In the past, feedthrough filter capacitors for heart pacemakers and thelike have typically been constructed by preassembly of the discoidalcapacitor with a terminal pin subassembly which includes the conductiveterminal pin and ferrule. More specifically, the terminal pinsubassembly is prefabricated to include one or more conductive terminalpins supported within the conductive ferrule by means of a hermeticallysealed insulator ring or bead. See, for example, the terminal pinsubassemblies disclosed in U.S. Pat. Nos. 3,920,888, 4,152,540;4,421,947; and 4,424,551. The terminal pin subassembly thus defines asmall annular space or gap disposed radially between the inner terminalpin and the outer ferrule. A small discoidal capacitor of appropriatesize and shape is then installed into this annular space or gap, inconductive relation with the terminal pin and ferrule, e.g., by means ofsoldering or conductive adhesive. The thus-constructed feedthroughcapacitor assembly is then mounted within an opening in the pacemakerhousing, with the conductive ferrule in electrical and hermeticallysealed relation in respect of the housing, shield or container of themedical device.

Although feedthrough filter capacitor assemblies of the type describedabove have performed in a generally satisfactory manner, such filtercapacitor assemblies may be susceptible to high voltage arcing betweenthe inner diameter and outer diameter of the capacitor, particularlyalong the bottom of the capacitor.

The present teachings provide a feedthrough filter capacitor assembly ofthe type used, for example, in implantable medical devices such as heartpacemakers and the like, wherein the filter capacitor is designed toinhibit high voltage arcing along the bottom of the capacitor.

SUMMARY

In various exemplary embodiments, the present disclosure relates to amethod of assembling a filtered feedthrough assembly. The methodincludes providing a capacitor having a top portion, a bottom portion,an outer diameter portion and an inner diameter portion. The innerdiameter portion defines at least one aperture extending from the topportion to the bottom portion. An insulative member is fixedly attachedto the bottom portion of the capacitor and is configured to inhibit highvoltage arcing. The method includes inserting at least one terminal pinwithin a ferrule and fixedly securing the capacitor with attachedinsulative member within the ferrule, wherein the at least one terminalpin extends through the opening and extends through the at least oneaperture.

In further various exemplary embodiments, the present disclosure relatesto a capacitor assembly for use in a filtered feedthrough for animplantable medical device. The capacitor assembly includes a capacitorhaving a top portion, a bottom portion, an outer diameter portion and aninner diameter portion, wherein the inner diameter portion defines atleast one aperture extending from the top portion to the bottom portion.The capacitor includes a plurality of conductive plates. An outerdiameter termination material is applied to the outer diameter portionof the capacitor and electrically couples a first subset of theplurality of conductive plates. The outer diameter termination materialis absent from an outer diameter lower portion of the outer diameterportion adjacent the bottom portion of the capacitor. An inner diametertermination material is applied to the inner diameter portion of thecapacitor and electrically couples a second subset of the plurality ofconductive plates. The inner diameter termination material is absentfrom an inner diameter lower portion of the inner diameter portionadjacent the bottom portion of the capacitor.

In further various exemplary embodiments, the present disclosure relatesto a method of assembling a filtered feedthrough assembly. The methodincludes providing a capacitor having a top portion, a bottom portion,an outer diameter portion and an inner diameter portion. The innerdiameter portion defines at least one aperture extending from the topportion to the bottom portion. The capacitor includes a plurality ofconductive plates. An outer diameter termination material on the outerdiameter portion of the capacitor electrically couples a first subset ofthe plurality of conductive plates. The outer diameter terminationmaterial is absent from an outer diameter lower portion of the outerdiameter portion adjacent the bottom portion of the capacitor. An innerdiameter termination material on the inner diameter portion of thecapacitor electrically couples a second subset of the plurality ofconductive plates. The inner diameter termination material is absentfrom an inner diameter lower portion of the inner diameter portionadjacent the bottom portion of the capacitor. The method includesinserting at least one terminal pin within a ferrule and fixedlysecuring the capacitor with attached insulative member within theferrule, wherein the at least one terminal pin extends through theopening and extends through the at least one aperture.

Further areas of applicability of the present disclosure will becomeapparent from the detailed description, the claims and the drawings. Thedetailed description and specific examples are intended for purposes ofillustration only and are not intended to limit the scope of thedisclosure.

BRIEF DESCRIPTION OF DRAWINGS

The present disclosure will become more fully understood from thedetailed description and the accompanying drawings, wherein:

FIGS. 1 and 2 are isometric and cross-sectional views, respectively, ofa known unipolar (single pin) feedthrough assembly prior to attachmentof a discrete discoidal capacitor;

FIGS. 3-5 illustrate a prior art method of attaching a discretediscoidal capacitor to the feedthrough assembly shown in FIGS. 1 and 2;

FIGS. 6-13 are cross-sectional views of a discrete discoidal capacitorwith a fixedly attached insulative member for use in a unipolar (singlepin) filtered feedthrough assembly according to various exemplaryembodiments of the present disclosure;

FIG. 14 is a cross-sectional view of a unipolar (single pin) filteredfeedthrough assembly with an attached discrete discoidal capacitor thatincludes a fixedly attached insulative member according to variousexemplary embodiments of the present disclosure;

FIG. 15 is a cross-sectional view of a unipolar (single pin) filteredfeedthrough assembly according to various exemplary embodiments of thepresent disclosure;

FIG. 16 is a cross-sectional view of a unipolar (single pin) filteredfeedthrough assembly with an attached discrete discoidal capacitor thatincludes a fixedly attached insulative member according to variousexemplary embodiments of the present disclosure;

FIG. 17 is an exploded view of a multipolar (multiple pin) filteredfeedthrough assembly illustrating the attachment of a monolithicdiscoidal capacitor that includes a fixedly attached insulative memberin accordance with various exemplary embodiments of the presentdisclosure;

FIG. 18 is a perspective view of a partially disassembled implantablemedical device; and

FIG. 19 is an isometric cutaway view of an implantable medical deviceincorporating the multipolar (multiple pin) filtered feedthroughassembly of FIG. 17.

DESCRIPTION

The following description is merely exemplary in nature and is in no wayintended to limit the disclosure, its application, or uses. For purposesof clarity, the same reference numbers will be used in the drawings toidentify similar elements. As used herein, the phrase at least one of A,B, and C should be construed to mean a logical (A or B or C), using anon-exclusive logical or. It should be understood that steps within amethod can be executed in different order without altering theprinciples of the present disclosure.

FIGS. 1 and 2 are isometric and cross-sectional views, respectively, ofa known unipolar (single pin) feedthrough assembly 100 having a terminalpin 102 extending therethrough. Assembly 100 comprises a generallycylindrical ferrule 104 having a cavity through which pin 102 passes.Ferrule 104 is made of an electrically conductive material (e.g.,titanium alloy) and is configured to be fixedly coupled (e.g., welded)to the container of a medical device as described below in conjunctionwith FIGS. 18-19. An insulating structure 106 is disposed within ferrule104 to secure pin 102 relative to ferrule 104 and to electricallyisolate pin 102 from ferrule 104. Insulating structure 106 comprises asupporting structure 108 and a joint-insulator sub-assembly 110, both ofwhich are disposed around terminal pin 102. As will be more fullydescribed below, joint-insulator sub-assembly 110 acts as an insulativeseal and can take the form of, for example, a braze joint. Supportingstructure 108 is made of a non-conductive material (e.g., polyimide) andrests on an inner ledge 112 provided within ferrule 104. As will be seenin FIG. 3, a discrete discoidal capacitor 150 can be threaded overterminal pin 102 and fixedly coupled to supporting structure 108 toattach the capacitor to feedthrough assembly 100.

As can be seen in FIG. 2, braze joint 110 comprises three maincomponents: an insulator ring 114 (e.g., made from a ceramic material)that insulates pin 102 from ferrule 104, a pin-insulator braze 116(e.g., made from gold) that couples insulating ring 114 to pin 102, andan insulator-ferrule braze 118 (e.g., made from gold) that couplesinsulating ring 114 to ferrule 104. Braze joint 110 is exposed along theunderside of ferrule 104. When ferrule 104 is fixedly coupled to thecontainer of the medical device, the lower portion of ferrule 104, andthus the lower portion of braze joint 110, can be exposed to bodyfluids. For this reason, it is important that braze joint 110 forms ahermetic seal between ferrule 104 and terminal pin 102. Braze joint 110can be leak tested. To permit this test to be performed, an aperture 120(FIG. 1) is provided through ferrule 104 to the inner annular cavityformed by the outer surface of braze joint 110, the lower surface ofsupporting structure 108, and the inner surface of ferrule 104. A gas isdelivered through aperture 120 into the inner annular cavity, andaperture 120 is plugged. Preferably, a gas of low molecular weight(e.g., helium or hydrogen) is chosen so that it can easily penetratesmall cracks in braze joint 110. Feedthrough 100 is then monitored forthe presence of the gas proximate braze joint 110 by way of, forexample, a mass spectrometer. If no gas is detected, it is concludedthat braze joint 110 has formed a satisfactory seal.

Terminal pin 102 provides a conductive path from the interior of amedical device (not shown) to one or more lead wires exterior to themedical device. As described previously, these lead wires are known toact as antennae that collect stray electromagnetic interference (EMI)signals, which can interfere with the proper operation of the device. Tosuppress and/or transfer such EMI signals to the container of themedical device, a discrete discoidal capacitor can be attached tofeedthrough assembly 100. In particular, the capacitor can be disposedaround and electrically coupled to terminal pin 102 and fixedly coupledto supporting structure 108. FIGS. 3-5 illustrate a known manner ofattaching a discrete discoidal capacitor 150 to feedthrough assembly 100shown in FIGS. 1 and 2. The attachment method commences as a ring-shapedpreform 152 of non-conductive epoxy is threaded over terminal pin 102(indicated in FIG. 3 by arrow 154). Capacitor 150 is then threaded overpin 102 and positioned against preform 152 such that preform 152 issandwiched between capacitor 150 and supporting structure 108. Next,feedthrough assembly 100 is placed within a curing oven and heated to apredetermined temperature (e.g., approximately 175 degrees Celsius) tothermally cure preform 152 (indicated in FIG. 4 by arrows 156) and thusphysically couple capacitor 150 to supporting structure 108.

During curing, preform 152 melts and disperses under the weight ofcapacitor 150, which moves downward toward supporting structure 108.Preform 152 disperses along the annular space provided between thebottom surface of capacitor 150 and the upper surface of supportingstructure 108 to physically couple capacitor 150 and supportingstructure 108 as described above. In addition, preform 152 can disperseupward into the annular space provided between the inner surface ofcapacitor 150 and outer surface of terminal pin 102 (shown in FIG. 5 at158). Dispersal of preform 152 in this manner can interfere with theproper electrical coupling of capacitor 150 to terminal pin 102. Also,during curing, preform 152 can disperse downward into insulatingstructure 110 (shown in FIG. 5 at 160). This dispersal can result inpreform 152 covering any cracks that have formed through braze joint 110and, consequently, prevent the accurate leak testing of feedthroughassembly 100.

Arcing between the inner surface and outer surface of the capacitor 150can occur (for example, along the bottom surface of the capacitor 150)in the presence of the high voltage associated with the feedthroughassembly 100. In addition to the limitations associated with utilizingepoxy preforms 152 described above, epoxy preforms 152 can beineffective for inhibiting this high voltage surface arcing along thebottom of the capacitor 150. The epoxy preform 152 tends to outgas andhave excessive weight loss when subjected to the heat treatmentassociated with electrically connecting the terminal pin 102 with theinner surface and the ferrule 104 with the outer surface of thecapacitor 150, e.g., with high-temperature solder. Referring now to FIG.6, a cross-sectional view of a capacitor 200 that inhibits surfacearcing according to various exemplary embodiments of the presentdisclosure is illustrated. The capacitor 200 includes a top portion 201,a bottom portion 203, an outside diameter portion 205 and an innerdiameter portion 207. Fixedly attached to the bottom portion 203 ofcapacitor 200 is an insulative member 210. The insulative member 210illustrated in FIG. 6 includes an adhesive 212 and a base member 214.The adhesive 212 adheres or otherwise attaches the base member 214 tothe bottom portion 203 of the capacitor 200. The adhesive 212 can be,for example, a glass material, a polyimide material, or a combination ofone or more of these materials. The base member 214 can be made of aceramic material (such as a low temperature co-fired ceramic (“LTCC”) oralumina), a plastic material (such as polyaryletheretherketone(“PEEK”)), a polyimide material, a glass material, or a combination ofone or more of these materials. Insulative member 210 essentially bondswith the bottom portion 203 of the capacitor 200 to form a unitarystructure. Insulative member 210 inhibits high voltage arcing along thebottom portion 203 of the capacitor, for example, by increasing thelength of the surface that an arc must travel between inner diameterportion 207 and outer diameter portion 205, as well as preventing adirect line of sight between the terminal pin 102 and ferrule 104.

In the exemplary embodiment illustrated in FIG. 7, capacitor 200includes an insulative member 210 that substantially covers the entiresurface area of the bottom portion 203 of the capacitor 200 and extendsaround the radius and into contact with the outer diameter 205 of thecapacitor 200. Insulative member 210 can be an insulative coating, e.g.,made of a non-conductive epoxy, a glass material, a plastic material, apolyimide material, or a combination of one or more of these materials.Furthermore, the insulative member 210 shown in FIG. 7 can include abase member adhered to the bottom portion 203, similar to thatillustrated in FIG. 6, in which the base member extends around theradius and into contact with the outer diameter 205 of the capacitor200.

In the exemplary embodiment illustrated in FIG. 8, capacitor 200includes an insulative member 210 that covers only a portion of thesurface area of the bottom portion 203 of the capacitor 200 and extendsaround the radius and into contact with the outer diameter 205 of thecapacitor 200. Insulative member 210 can be an insulative coating, e.g.,made of a glass material, a polyimide material, or a combination of oneor more of these materials. Furthermore, the insulative member 210 shownin FIG. 8 can include a base member adhered to the bottom portion 203,similar to that illustrated in FIG. 6, in which the base member extendsaround the radius and into contact with the outer diameter 205 of thecapacitor 200.

In additional exemplary embodiments of the present disclosure, acapacitor 200 includes an insulative member 210 that substantiallycovers the entire surface area of the bottom portion 203 of thecapacitor 200, as shown in FIG. 9. Insulative member 210 can be aninsulative coating, e.g., made of a glass material, a plastic material,a polyimide material, or a combination of one or more of thesematerials.

Referring now to FIG. 10, a cross-sectional view of a capacitor 200 thatinhibits surface arcing according to various exemplary embodiments ofthe present disclosure is illustrated. The capacitor 200 includes a topportion 201, a bottom portion 203, an outside diameter portion 205 andan inner diameter portion 207. Fixedly attached to the bottom portion203 of capacitor 200 is an insulative member 210. The insulative member210 illustrated in FIG. 10 includes an adhesive 212 and a base member214. The adhesive 212 adheres or otherwise attaches the base member 214to the bottom portion 203 of the capacitor 200. The adhesive 212 can be,for example, a glass material, a polyimide material, or a combination ofone or more of these materials. The base member 214 can be made of analumina material, a plastic material, a polyimide material, a glassmaterial, a ceramic material, or a combination of one or more of thesematerials. Insulative member 210 essentially bonds with the bottomportion 203 of the capacitor 200 to form a unitary structure. Insulativemember 210 substantially covers the entire surface area of the bottomportion 203 of the capacitor 200 and extends around the radius and intocontact with the outer diameter 205 of the capacitor 200. The portionthat extends into contact with the bottom portion 203 of the capacitor200 can be the adhesive 212, as shown in FIG. 10, or the base member 214(not shown). Insulative member 210 inhibits high voltage arcing alongthe bottom portion 203 of the capacitor, for example, by increasing thelength of the surface that an arc must travel between inner diameterportion 207 and outer diameter portion 205, as well as preventing adirect line of sight between the terminal pin 102 and ferrule 104.

Referring now to FIG. 11, a cross-sectional view of a capacitor 200 thatinhibits surface arcing according to additional exemplary embodiments ofthe present disclosure is illustrated. The insulative member 210 shownin FIG. 11 can comprise a base member that is fixedly attached to thebottom portion 203 of the capacitor 200. For example, the insulativemember 210 can comprise a low temperature co-fired ceramic (“LTCC”)material that is laminated to the bottom portion 203 of capacitor 200.It is contemplated that other insulative members 210, such as those madeof an alumina material, a plastic material, a polyimide material, aglass material, a ceramic material, or a combination of one or more ofthese materials, can be utilized. Furthermore, the insulative member 210can be fixedly attached to the bottom portion 203 of the capacitor 200by materials and/or processes other than lamination, such as a glassmaterial, a polyimide material, or a combination of one or more of thesematerials. One of the benefits associated with utilizing a separateinsulative member 210 fixedly attached to the capacitor 200 is that theinsulative layer is substantially uniform across the surface area of thebottom portion 203.

In further additional exemplary embodiments of the present disclosure, acapacitor 200 can have an unterminated portion 225 on one of or each ofthe outer diameter and inner diameter portions 205, 207 proximate to thebottom portion 203 of the capacitor 200, as illustrated in FIG. 12. Theouter and inner diameter portions 205, 207 of capacitor 200 are coatedwith a conductive termination material 220 a and 220 b, respectively.Termination material 220 a electrically couples one of the two sets ofthe electrode plates that form the capacitor with the outer diameterportion 205. Termination material 220 b electrically couples the otherone of the two sets of the electrode plates that form the capacitor withthe inner diameter portion 207. In a typical capacitor, the terminationmaterial extends along the full length of the inner and outer diameterportions of the capacitor 200. The exemplary capacitor 200 illustratedin FIG. 12 includes unterminated portions 225 on each of the outerdiameter and inner diameter portions 205, 207 proximate to the bottomportion 203, although only one of the inner and outer diameter portionsincluding an unterminated portion is within the scope of the presentdisclosure. In this construction, capacitor 200 inhibits high voltagearcing along the bottom portion 203 of the capacitor, for example, byincreasing the length of the surface that an arc must travel between theinner diameter portion 207, i.e., termination material 220 b, and outerdiameter portion 205, i.e., termination material 220 a.

Similar to the capacitor illustrated in FIG. 12, FIG. 13 illustrates acapacitor 200 with unterminated portions 225 for inhibiting high voltagearcing along the bottom portion 203 of the capacitor. As shown in FIG.13, capacitor 200 includes a tapered inner diameter portion 202 fromwhich termination material 220 b is absent. The absence of terminationmaterial 220 b in tapered inner diameter portion 202 inhibits highvoltage arcing along the bottom portion 203 of the capacitor 200, forexample, by increasing the length of the surface that an arc must travelbetween the inner diameter portion 207, i.e., termination material 220b, and outer diameter portion 205, i.e., termination material 220 a.

Referring now to FIG. 14, a filtered feedthrough assembly 300 accordingto various exemplary embodiments of the present disclosure isillustrated. Filtered feedthrough assembly 300 is unipolar (single pin)and has a terminal pin 302 extending therethrough. Assembly 300comprises a generally cylindrical ferrule 304 having a cavity throughwhich pin 302 passes. Ferrule 304 is made of an electrically conductivematerial (e.g., titanium alloy) and is configured to be fixedly coupled(e.g., welded) to the container of a medical device as described belowin conjunction with FIG. 19. An insulating structure comprisingsupporting structure 308 and a joint-insulator sub-assembly 310 isdisposed within ferrule 304 to secure pin 302 relative to ferrule 304and to electrically isolate pin 302 from ferrule 304. Both of thesupporting structure 308 and a joint-insulator sub-assembly 310 aredisposed around terminal pin 302. The joint-insulator sub-assembly 310acts as an insulative seal and can take the form of, for example, abraze joint. Supporting structure 308 is made of a non-conductivematerial (e.g., polyimide, polyetheretherketone (PEEK) or similarmaterial) and rests on an inner ledge 312 provided within ferrule 304.As will be seen, a discrete discoidal capacitor can be threaded overterminal pin 302 and fixedly coupled to supporting structure 308 toattach the capacitor to feedthrough assembly 300. Alternatively, thesupporting structure 308 can be eliminated from the assembly and thediscrete discoidal capacitor can rest on inner ledge 312 directly, as isdescribed in U.S. patent application Ser. No. 12/183,922, filed Jul. 31,2008, entitled “Novel Capacitive Elements And Filtered FeedthroughAssemblies For Implantable Medical Devices,” U.S. patent applicationSer. No. 12/183,940, filed Jul. 31, 2008, entitled “Novel CapacitiveElements And Filtered Feedthrough Assemblies For Implantable MedicalDevices” and U.S. patent application Ser. No. 12/183,953, filed Jul. 31,2008, entitled “Novel Capacitive Elements And Filtered FeedthroughAssemblies For Implantable Medical Devices,” which are incorporatedherein in their entirety.

Braze joint 310 comprises three main components: an insulator ring 314(e.g., made from a ceramic material) that insulates pin 302 from ferrule304, a pin-insulator braze 316 (e.g., made from gold) that couplesinsulating ring 314 to pin 302, and an insulator-ferrule braze 318(e.g., made from gold) that couples insulating ring 314 to ferrule 304.Braze joint 310 is exposed along the underside of ferrule 304. Whenferrule 304 is fixedly coupled to the container of the medical device,the lower portion of ferrule 304, and thus the lower portion of brazejoint 310, can be exposed to body fluids. For this reason, it isimportant that braze joint 310 forms a hermetic seal between ferrule 304and terminal pin 302, which can be leak tested, as described above.

Terminal pin 302 provides a conductive path from the interior of amedical device (not shown) to one or more lead wires exterior to themedical device. As described previously, these lead wires are known toact as antennae that collect stray electromagnetic interference (EMI)signals, which can interfere with the proper operation of the device. Tosuppress and/or transfer such EMI signals to the container of themedical device, a discrete discoidal capacitor 350 with fixedly attachedinsulative member 360 can be attached to feedthrough assembly 300. Inparticular, the capacitor 350 can be disposed around and electricallycoupled to terminal pin 302 and fixedly coupled to supporting structure308, described more fully below.

Referring now to FIGS. 15-16, an alternative filtered feedthroughassembly 361 according to various exemplary embodiments of the presentdisclosure is illustrated. A support structure 380 is sized andconfigured to be received within ferrule 364. In the illustratedexample, support structure rests upon an inner ledge 372 provided withinferrule 364. Support structure 380 can be designed for use in aunipolar, i.e., single pin, feedthrough assembly or a multipolar, i.e.,multiple pin, feedthrough assembly. The design differences between aunipolar and multipolar support structure 380 are minor and essentiallyequate to including the correct number of openings within supportstructure 380 to accommodate the number of terminal pin(s) 362 in thefeedthrough. The support structure 380 can be similar to those describedin U.S. patent application Ser. No. 12/368,847, filed Feb. 10, 2009,entitled “Filtered Feedthrough Assembly And Associated Method,” which isherein incorporated in its entirety.

The filtered feedthrough assembly 361 according to various exemplaryembodiments can be assembled as follows. The joint-insulatorsub-assembly 370 is disposed within ferrule 364 to secure pin 362relative to ferrule 364 and to electrically isolate pin 362 from ferrule364. Support structure 380 can then be inserted within ferrule 364 suchthat terminal pin 362 extends through the opening therein. The openingof support structure 380 can be sized so as to mate with terminal pin362 in a secure fashion. A partially assembled filtered feedthroughassembly 361 according to various exemplary embodiments of the presentdisclosure is illustrated in FIG. 15.

Capacitor 390 with fixedly attached insulative member 391 is theninserted at least partially within the ferrule 364 such that terminalpin 362 extends through, and a projection 382 of support structure 380is partially received within, aperture 395. In some exemplaryembodiments, the projection 382 and aperture 395 are sized such that theprojection 382 is tightly secured in the aperture 395, e.g., to create aseal between projection 382 and aperture 395. In this manner, supportstructure 380 can be physically coupled to capacitor 390 without the useof non-conductive epoxy or other compound as in the prior art, which notonly simplifies the assembly process, but also prevents the intrusion ofthe non-conductive epoxy into the joint-insulator sub-assembly 370.Furthermore, projection 382 can be sized and positioned such that theterminal pin 362 is substantially centered within aperture 395, whichwill assist in the formation of a reliable electrical connection betweencapacitor 390 and terminal pin 362.

After placement of capacitor 390 within ferrule 364, the inner diameterportion 396 of capacitor 390 is electrically coupled to the terminal pin362, e.g., by means of solder or conductive epoxy 397. Similarly, theouter diameter portion 398 of capacitor 390 is electrically coupled tothe ferrule 364, e.g., by means of solder or conductive epoxy 399.Support structure 380, and specifically the coupling of aperture 395 andprojection 382, inhibits or prevents the flow of solder or conductiveepoxy 397, 399 into the joint-insulator sub-assembly 370. A fullyassembled filtered feedthrough assembly 361 according to variousexemplary embodiments of the present disclosure is illustrated in FIG.16.

FIG. 17 illustrates the attachment of a monolithic discoidal capacitor400, which has already been fixedly attached with insulative member 401in one of the manners described above, to a multipolar feedthroughassembly 402 in accordance with various exemplary embodiments of thepresent invention. Filtered feedthrough assembly 402 comprises a ferrule406 and an insulating structure 404 disposed within ferrule 406.Filtered feedthrough assembly 402 guides an array of terminal pins 405through the container of a medical device to which ferrule 404 iscoupled (shown in FIG. 19). As described above, terminal pin array 405and the lead wires to which array 405 is coupled can act as an antennaand collect undesirable EMI signals. Monolithic discoidal capacitor 400can be attached to feedthrough assembly 402 to provide EMI filtering.Capacitor 400 and insulative member 401 is provided with a plurality ofterminal pin-receiving apertures 410 therethrough. Capacitor 400 withattached insulative member 401 is inserted over terminal pin array 405such that each pin in array 405 is received by a different aperture 410and placed in an abutting relationship with insulating structure 404. Ifdesired, one terminal pin in array 405 can be left unfiltered as shownin FIG. 17 to serve as an RF antenna. Support structure 480 is providedbetween insulating structure 404 and capacitor 400 and insulative member401. Capacitor 400 and insulative member 401 can be coupled to supportstructure 480, such as by projections 481 on support structure 480 beingsecurely received within terminal pin-receiving apertures 410, similarlyto that discussed above in U.S. patent application Ser. No. 12/368,847.Furthermore, a sleeve 482 can be included on support structure 480 toassist in the isolation of the unfiltered pin 405U from capacitor 400.

FIG. 18 is an exploded view of an implantable medical device (e.g., apulse generator) 450 coupled to a connector block 451 and a lead 452 byway of an extension 454. The proximal portion of extension 454 comprisesa connector 456 configured to be received or plugged into connectorblock 451, and the distal end of extension 454 likewise comprises aconnector 458 including internal electrical contacts 460 configured toreceive the proximal end of lead 452 having electrical contacts 462thereon. The distal end of lead 452 includes distal electrodes 464,which can deliver electrical pulses to target areas in a patient's body(or sense signals generated in the patient's body, e.g., cardiacsignals).

After a capacitor 400 and insulative member 401 have been attached tofeedthrough assembly 402 in the manner described above, assembly 402 canbe welded to the housing of an implantable medical device 450 as shownin FIG. 19. Medical device 450 comprises a container 452 (e.g. titaniumor other biocompatible material) having an aperture 454 therein throughwhich feedthrough assembly 402 is disposed. As can be seen, eachterminal pin in array 405 has been trimmed and is electrically connectedto circuitry 456 of device 450 via a plurality of connective wires 458(e.g., gold), which can be coupled to terminal pin array 405 by wirebonding, laser ribbon bonding, or the like. After installation,feedthrough assembly 402 and capacitor 400 collectively function topermit the transmission of relatively low frequency electrical signalsalong the terminal pins in array 405 to circuitry 456 while shuntingundesired high frequency EMI signals to container 452 of device 450.

The broad teachings of the disclosure can be implemented in a variety offorms. Therefore, while this disclosure includes particular examples,the true scope of the disclosure should not be so limited since othermodifications will become apparent upon a study of the drawings, thespecification, and the following claims.

What is claimed is:
 1. A capacitor assembly for use in a filteredfeedthrough for an implantable medical device, comprising: a capacitorhaving a top portion, a bottom portion, an outer diameter portion and aninner diameter portion, wherein the inner diameter portion defines atleast one aperture extending from the top portion to the bottom portion,the capacitor including a plurality of conductive plates; an outerdiameter termination material applied to the outer diameter portion ofthe capacitor, the outer diameter termination material electricallycoupling a first subset of the plurality of conductive plates, the outerdiameter termination material being absent from an outer diameter lowerportion of the outer diameter portion adjacent the bottom portion of thecapacitor; and an inner diameter termination material applied to theinner diameter portion of the capacitor, the inner diameter terminationmaterial electrically coupling a second subset of the plurality ofconductive plates, the inner diameter termination material being absentfrom an inner diameter lower portion of the inner diameter portionadjacent the bottom portion of the capacitor.
 2. The capacitor assemblyof claim 9, wherein the inner diameter lower portion comprises a taperedinner diameter portion.